Under GST it might happen that the taxable person may pay integrated tax instead of central tax plus state tax and vice versa because of incorrect application of the place of supply provisions. In such cases, while making the appropriate payment of tax, interest will not be charged and the refund claim of the wrong tax paid earlier will be entertained without subjecting it to the provision of unjust enrichment.

Case laws are available but that is a matter of litigation. See my reply against Issue ID No.115288 dated 6.8.19. There is also a judgement of Gujarat Hight Court which has held that last date for availing ITC for 17-18 is 31.8.19 as GSTR 3 B is not a return.

The case law was not handy with me. Had the case law been handy, I would have shared with you in this forum. I believe in, "Knowledge is power, if shared'. If knowledge is not shared, it may become outdated tomorrow. Still I receive so many calls pertaining to Central Excise & Service Tax and I do not hide or hesitate. It gives me immense pleasure to share any type of information with any person may be party or professional. Every information is not always ready. There is no gap between my word and deed. I hope you understand me very well.